The human eye functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of a crystalline lens onto a retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and the lens.
When age or disease causes the lens to become less transparent (e.g., cloudy), vision deteriorates because of the diminished light, which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. An accepted treatment for this condition is surgical removal of the lens from the capsular bag and placement of an artificial intraocular lens (IOL) in the capsular bag. In the United States, the majority of cataractous lenses are removed by a surgical technique called phacoemulsification. During this procedure, an opening (capsulorhexis) is made in the anterior side of the capsular bag and a thin phacoemulsification-cutting tip is inserted into the diseased lens and vibrated ultrasonically. The vibrating cutting tip liquefies or emulsifies the lens so that the lens may be aspirated out of the capsular bag. The diseased lens, once removed, is replaced by an IOL.
After cataract surgery to implant an IOL, the optical result may be suboptimal or may need adjustment over time. For example, shortly after the procedure, it may be determined that the refractive correction is erroneous leading to what is sometimes called “refractive surprise.” Also for example, long after the procedure, it may be determined that the patient needs or desires a different correction, such as a stronger refractive correction, an astigmatism correction, or a multifocal correction.
In each of these cases, a surgeon may be reluctant to attempt removal of the suboptimal IOL from the capsular bag and replacement with a new IOL. In general, manipulation of the capsular bag to remove an IOL risks damage to the capsular bag including posterior rupture. This risk increases over time as the capsular bag collapses around the IOL and tissue ingrowth surrounds the haptics of the IOL. Thus, it would be desirable to be able to correct or modify the optical result without the need to remove the IOL or manipulate the capsular bag.
A variety of secondary lenses have been proposed to address the aforementioned drawbacks. For example, one possible solution includes a secondary lens that resides anterior to the capsular bag with haptics that engage the ciliary sulcus. While this design may have the advantage of avoiding manipulation of the capsular bag, its primary disadvantage is engaging the ciliary sulcus. The ciliary sulcus is composed of soft vascularized tissue that is susceptible to injury when engaged by haptics or other materials. Such injury may result in complications such as bleeding, inflammation and hyphema. Thus, in general, it may be desirable to avoid placing a secondary lens in the ciliary sulcus to avoid the potential for complications.
Another potential solution may include a lens system that avoids the potential problems associated with the ciliary sulcus. The lens system may include a primary lens and a secondary lens, where the secondary lens may be attached to the primary lens, both within the capsular bag. The primary lens may have a recess into which an edge of the secondary lens may be inserted for attachment. The recess is preferably located radially outwardly of the opening (capsulorhexis) in the capsular bag to avoid interfering with light transmission. To attach the secondary lens in-situ, the capsular bag must be manipulated around the perimeter of the capsulorhexis to gain access to the recess in the primary lens. As stated previously, manipulation of the capsular bag may be undesirable given the risks associated therewith. Therefore, while such lens systems may avoid the potential for injury to the ciliary sulcus by implanting both the primary lens and the secondary lens in the capsular bag, these systems do not avoid manipulation of the capsular bag to attach the secondary lens.
Thus, there remains a need for an IOL system and method that allows for correction or modification of the optical result using a lens that can be attached to a base or primary lens without the need manipulate the capsular bag.